X-ray installation



April 3, 1934. BOUWERS 1,953,391

X-RAY INSTALLATION Filed March 11 1929 Patented Apr. 3, 1934 1,953,391 X-RAY INSTALLATION Albert Bouwers, Eindhoven, Netherlands, as-

signor to N. V. Philips Gloeilampenfabrieken;

Eindhoven,

Netherlands, a limited-liability company of the Netherlands 7 Claims. (Cl. 250-34) This invention has reference to an X-ray installation.

The dimensions of an X-ray tube are'determined essentially by the value of the operating voltage of the tube. As a matter of fact, the

length of the insulation between the two electrodes must be sufficient to avoid flash-over. The distance of the X-ray tube relative to the remaining parts of the X-ray installation, for example to the grounded screen by which the X-ray tube is often surrounded, is likewise determined by the value of the operating voltage. Thus the dimensions of an X-ray tube as well as of an X-ray installation are often necessarily larger than may be advisable to insure easy manipulation.

According to my invention, this difficulty is avoided by providing in an X-ray installation comprising an X-ray tube, a compressed gas or gas mixture between the X-ray tube and a closed envelope surrounding the latter. The envelope may be of metal and can partially coincide with part of the wall of the X-ray tube. Preferably, a gas valve is mounted in the envelope or in a space communicating therewith.

It is an object of the invention to provide a protective envelope around an X-ray tube Without necessitating unduly large dimensions thereof.

Another object of the invention is to reduce the danger of flash-over between the electrodes of an X-ray tube and between each of these electrodes and the conductors in the vicinity thereof.

A further object of the invention is to increase the admissible voltage of an X-ray installation.

According to the invention the space between an X-ray tube and a closed protective envelope, surrounding same, is filled with a compressed gas or gas mixture. The envelope may be of metal and may be mechanically connected to a metallic portion of the tube wall surrounding the discharge space between the electrodes. The pressure of the compressed gas increases the break down voltage of the Y-ray installation since the dielectric strength of gases above 1 atmosphere is very considerably increased at higher pressures.

The X-ray installation may be so constructed that the X-ray tube is cut out of th electric circuit when the pressure of the gas or gas mixture falls below a predetermined value. For this purpose the envelope for example may have mounted on it a contact which, when the pressure of the 55 gas or gas-mixture falls below a predetermined value, closes a circuit which comprises the exciting coil of a switch inserted in the supply circuit of the transformer.

Alternatively, the space between the X-ray tube and the envelope may be connected to a pump which is brought into operation when the pressure of the gas or gas mixture falls below a predetermined value.

The invention will be more clearly understood by reference to the accompanying drawing which diagrammatically illustrates two embodiments thereof. 1

Referring to Figural, the X-ray tube 1, which comprises an incandescent cathode 2 and an anticathode 3, is surrounded by a closed envelope 4 in which the X-ray tube is supported by rings 5. The X-rays can emerge from. the tube through a window 6 providedin the envelope. The X-ray tubeis supplied from a transformer 7 the primary winding of which is adapted for connection to a suitable alternating current supply circuit.

The envelope 4 and the X-ray tube 1 have enclosed between them a compressed gas or gas mixture which may be constituted, for example, by air and which may be supplied through a valve 8. This permits designing the X-ray tube so that the dimensions are smaller than in the case when an envelope with compressed gas is not provided; and an easier manipulation of the tube is thus secured.

The envelope 4 has mounted on it a pressure gauge 9 constituted, for example, by a mercurycontaining U-shaped tube. If the pressure of the gas enclosed within the envelope falls below a determined value, the mercury within the right arm of the manometer 9 will rise to such an extent that it makes contact with the rod 10 so that a circuit in which the exciting coil of a relay 11 is inserted, is closed. Thus the relay is excited and the primary of the transformer. is interrupted so that the X-ray tube is cut out of the electric circuit.

Referring to Figure 2, the part 13 of the wall of the X-ray tube 12 is of metal. This metal part is prolonged by two metal hoods 14. Again, the spaces between the hoods 14 and the X-ray tube are filled with a compressed gas or gas mixture and are in communication with each other by a tube of small diameter 15 which by a flexible tube 16 is connected to a manometer 1'7 and a pressure I 6 pump 18. The said manometer likewise contains a rod-shaped member 19 which as soon as the pressure of the gas enclosed between the envelope and the X-ray tube falls below a predetermined value, engages the mercury so that the supply cir- 1 10 cuit of the motor connected to the pump 18 is closed, the pump 18 is brought into operation and the pressure of the gas can be increased. The gas is prevented from flowing back by a valve 20. The pump .18 with its motor-can be constructed as a unit togetherwith the transformer bywhich the X-ray tube is supplied.

The member which responds to too low a pressure of the gas enclosed between the envelope and the X-ray tube need not necessarily be constituted by a U-shaped mercury-containing tube. It is also possible to use other contacts whichare closed when the pressure of the gas falls below a predetermined value.

What I claim is:

1. An X-ray installation comprising an X-ray tube and a closed envelope surrounding the tube, compressed gas being enclosed betwe'enthe X-ray tube and the said envelope.

2. An X-ray installation comprising an X-ray 'tube having a wall which is made partly of metal,

a closedenvelope surrounding the tube and mechanically connected with a metal "part of the tube wall, compressed gas being enclosed between insulating parts of the tube wall and the envelope.

3. An Xray installation comprising an 'X-ray tube having a wall having insulating portionscar- ,rying electrodes and a metallic portion surrounding the path of the discharge between said electrodes, a closed metallic envelope surrounding the tube in "spaced relation with said electrodes and said insulating portions and girding the said metallic portion of the wall, and 'compressed'gas enclosed in the space between saidme'tal lic envelope and the insulating portions of said tube wall.

4. AnX-ray installation, comprising an X-ray tube and a closed protective envelope surrounding the same .in spaced relation therewith and supporting the tube, "the break down potential between the high tension parts of thetube and the envelope being increased by the presence of compressed gas introduced into the space between the tube and the envelope.

5. An X-ray installation comprising an X-ray tube, an envelope surrounding said tube and containing a gas under pressure, said envelope having an opening and a valve connected to said envelope and cooperating with said opening, said valve permitting the introduction of gas through said aperture and preventing the escape of gas therethrough.

6. An X-ray installation comprising an X-ray tube, an envelope .surrounding said tube and containing a gas under pressure, pressure-responsive switching means and gas supplying means connected with said envelope and in communication with the-interior thereof, a part of said gas supplying means being connected with a driving mechanism, an electric circuit including said switching means and driving mechanism, said circuit upon closure by :said switching means in response to a decrease in gas pressure setting in operation :the mechanism and gas supplying means whereby the pressure vof the gas is restored to a predetermined value.

'1. An X-ray installation comprising an X-ray tube having a cathode and an anti-cathode and an envelope surrounding said tube, and containing a gas under pressure, a pressure-responsive switc'hconnec'ted with said envelope and in 'com- X mun'icationwith the interior thereof, a high voltage transformer having apriinary low voltage circuit and a secondary high voltage circuit, said secondary circuit including said X-ray tube, said primary circuit including a relay switch, an auxil- 11 iary circuit for said relay switch, said auxiliary circuit comprising said pressure-responsive switch and upon closure of the latter opening said relay switch.

ALBERT BOUWERS. 

